The present invention relates to an aqueous dispersion of a segmental copolymer, wherein films formed from the aqueous dispersion display an improved balance of properties related to hardness and softness, and to the segmental copolymer of which the aqueous dispersion is comprised.
Polymeric films are typically formed by deposition of a solution or dispersion of a polymer in a solvent or dispersing medium, respectively. Evaporation of the layer thus formed will result in a continuous film for some polymer compositions, but not for others. For example, a dispersion including polymeric particles, the polymeric chains of which have a glass transition temperature in the range of xe2x88x9240xc2x0 C. to 70xc2x0 C., may form a continuous film, with the likelihood of such formation increasing for polymers having Tg values near, or below, the temperature at which film formation is attempted, often room temperature. Unfortunately, films that are easily formed often exhibit poor hardness related properties. They tend to be xe2x80x9csoftxe2x80x9d and tacky. This tackiness translates into a tendency for the surface of the film to retain dirt particles that contact it. Tackiness also translates into xe2x80x9cblockxe2x80x9d, the tendency for two films to stick to one another, or for a single film to stick to itself. The softness further translates into unrecoverable deformation, called xe2x80x9cprintxe2x80x9d. xe2x80x9cPrintxe2x80x9d is observed when an object is placed upon a film and, upon removal, the imprint of the object does not go away.
It is, therefore, highly desirable to form films that have a xe2x80x9chardnessxe2x80x9d component. This hardness translates into films having surfaces that resist scratching, dirt pick-up, and block. Truly xe2x80x9chardxe2x80x9d films are difficult to achieve because the relatively high glass transition temperature, xe2x80x9cTgxe2x80x9d, required to produce such films renders the actual formation of films difficult or impossible. When these xe2x80x9chardxe2x80x9d films are achieved, for example, by adding high levels of a coalescent to an aqueous dispersion of a hard polymer, these films often are so dominated by the hardness characteristic that they fail to exhibit softness characteristics that can contribute to overall performance of the film. Hard films are often brittle films lacking the flexibility to elongate and bend, especially at low temperature (i.e., below 20xc2x0 C.), a common requirement during use.
The invention of U.S. Pat. No. 6,060,532 sought, for example, to provide coatings having a good balance of low temperature flexibility, tensile strength, and dirt pick up resistance. Low temperature flexibility is a xe2x80x9csoftnessxe2x80x9d characteristic, while tensile strength and dirt pick up resistance are characteristic of xe2x80x9chardnessxe2x80x9d. Coatings were formed from a binder polymer which was an elastomeric multi-stage emulsion polymer obtained by sequentially polymerizing, under emulsion polymerization conditions, a first monomer system free from polyethylenically unsaturated monomers, and which yields a first-stage polymer having a glass transition temperature from about xe2x88x9230xc2x0 C. to about xe2x88x9260xc2x0 C., and a second monomer system, likewise free from polyethylenically unsaturated monomers, and which yields a second-stage polymer, incompatible with the first-stage polymer, and having a glass transition temperature from 0xc2x0 C. to 60xc2x0 C. Used herein, these two-stage polymers are referred to a xe2x80x9csoft/hard elastomersxe2x80x9d, or xe2x80x9cSHExe2x80x9d polymers. While the SHE polymers of U.S. Pat. No. 6,060,532 did improve the balance of hard and soft properties over that of single stage polymers having similar overall compositions, there remained a need for yet further improvement in the hard/soft balance. It was further desired to achieve that improvement while maintaining excellent film formation behavior for aqueous binder systems completely free of coalescing agents, or containing only low levels of them.
We have, surprisingly, found that aqueous dispersions of segmental copolymers can be formed into films having an outstanding balance of properties related to hardness and softness. In particular, we have been able to produce comb copolymers and aqueous dispersions of comb copolymers by a commercially viable method and form them into films having an outstanding balance of properties related to hardness and softness. The polymers can, for example, be utilized in films cast onto substrate surfaces and in free standing films.
A first aspect of the present invention relates to an aqueous dispersion, comprising at least one segmental copolymer, wherein said aqueous dispersion has a Hard/Soft Balance Advantage value of at least 25%.
A second aspect of the present invention relates to a method of forming a film comprising the steps of:
(a) forming an aqueous dispersion of a segmental polymer;
(b) applying said aqueous dispersion to a substrate; and
(c) drying, or allowing to dry, said applied aqueous dispersion;
wherein said aqueous dispersion has a Hard/Soft Balance Advantage value of at least 25%.
A third aspect of the present invention relates to a method of forming a film comprising the steps of:
(a) forming an aqueous dispersion comprising a plurality of comb copolymer particles:
wherein said comb copolymer particles comprise a comb copolymer; and
wherein said comb copolymer comprises a backbone and at least one graft segment attached thereto;
(b) applying said aqueous dispersion to a substrate; and
(c) drying, or allowing to dry, said applied aqueous dispersion;
wherein said aqueous dispersion has a Hard/Soft Balance Advantage value of at least 25%.
A fourth aspect of the present invention relates to a film produced by the method of either the second aspect or the third aspect.
A further aspect relates to an aqueous dispersion wherein the comb copolymer is produced by a polymerization method comprising the steps of:
(a) forming a macromonomer aqueous emulsion comprising a plurality of water-insoluble particles of macromonomer, wherein said macromonomer comprises polymerized units of at least one first ethylenically unsaturated monomer, said macromonomer further having:
(i) a degree of polymerization of from 10 to 1000;
(ii) at least one terminal ethylenically unsaturated group;
(iii) less than 5 weight percent polymerized acid-containing monomer, based on the weight of said macromonomer; and
(iv) less than one mole percent of polymerized mercaptan-olefin compounds;
(b) forming a monomer composition comprising at least one second ethylenically unsaturated monomer; and
(c) combining at least a portion of said macromonomer aqueous emulsion and at least a portion of said monomer composition to form a polymerization reaction mixture; and
(d) polymerizing said macromonomer with said second ethylenically unsaturated monomer in the presence of an initiator to produce said plurality of comb copolymer particles.
In a still further aspect, the comb copolymer has a weight average molecular weight of 50,000 to 2,000,000.
In yet another aspect, the graft segment of the comb copolymer is derived, as a polymerized unit, from a macromonomer; wherein the graft segment comprises, as polymerized units, from 5 weight percent to 50 weight percent of a non-methacrylate monomer, based on the weight of the macromonomer.
In another aspect, the graft segment of the comb copolymer is derived, as a polymerized unit, from a macromonomer; wherein the graft segment comprises, as polymerized units, less than 5 weight percent acid containing monomer, based on the total weight of said macromonomer.
In another aspect, the graft segment of the comb copolymer is derived, as a polymerized unit, from a macromonomer, wherein said graft segment has a degree of polymerization of from 10 to 1,000, where the degree of polymerization of said graft segment is expressed as the degree of polymerization of said macromonomer.
In another aspect, the graft segment of the comb copolymer has a glass transition temperature of 30xc2x0 C. to 130xc2x0 C.
In another aspect, the backbone of the comb copolymer has a glass transition temperature of xe2x88x9290xc2x0 C. to 50xc2x0 C.
Used herein, the following terms have these definitions:
The xe2x80x9cbackbonexe2x80x9d of a polymer chain is a collection of polymerized monomer units attached to one another. The attachment is typically achieved by covalent bonding. xe2x80x9cNon-terminalxe2x80x9d monomer units are directly attached to at least two other monomer units. A xe2x80x9cterminalxe2x80x9d monomer unit resides at the end of the polymer chain and is directly attached to one other monomer unit. For example, the polymerized monomer units of the backbone may be derived from ethylenically unsaturated monomers.
A xe2x80x9clinearxe2x80x9d polymer (homopolymer or copolymer) is a polymer having a backbone that is not branched. As used herein, the term xe2x80x9clinearxe2x80x9d is also meant to include polymers wherein a minor amount of branching has occurred. For example, hydrogen abstraction may lead to branching during free radical polymerizations.
A xe2x80x9cbranchedxe2x80x9d polymer is a polymer having a first xe2x80x9cbackbone segmentxe2x80x9d that has other backbone segments (i.e., xe2x80x9cbranchesxe2x80x9d) chemically attached to it through a xe2x80x9cnon-terminalxe2x80x9d atom of the first backbone segment. Typically, this first backbone segment and all of the branches have the same, or similar, composition. Herein, the term xe2x80x9cbranchingxe2x80x9d is used to describe the structure of the backbone of the comb copolymer.
A xe2x80x9cpendantxe2x80x9d group is a group that is attached to the backbone of a polymer. The term pendant may be used to describe a group that is actually part of a polymerized monomer unit. For example, the hydroxyethyl group of a polymerized unit of 2-hydroxyethyl methacrylate may be referred to as a xe2x80x9cpendant hydroxyethyl groupxe2x80x9d, or as xe2x80x9cpendant hydroxy functionalityxe2x80x9d. It is also common to refer to large groups attached to a polymer backbone as xe2x80x9cpendantxe2x80x9d when those large groups are compositionally distinct from the backbone polymer. These large groups may themselves be polymer chains. For example, when a macromonomer becomes incorporated into a polymer chain by reaction with other monomers, the two carbons of its reactive double bond become part of the backbone, while the polymeric chain originally attached to the double bond of the macromonomer becomes a xe2x80x9cpendant groupxe2x80x9d that may, for example, have a molecular weight of 500 to 100,000. A xe2x80x9cpendantxe2x80x9d group may further be described as xe2x80x9cpendant toxe2x80x9d the backbone.
A xe2x80x9cterminalxe2x80x9d group resides at the end of the polymer chain and is chemically attached to a terminal monomer unit. A terminal group may, for example, have a composition distinct from the composition of the backbone of the polymer. A xe2x80x9cpendantxe2x80x9d group may occur in a xe2x80x9cterminalxe2x80x9d position. As such, a xe2x80x9cterminalxe2x80x9d group is a special case of a xe2x80x9cpendantxe2x80x9d group.
A xe2x80x9cmacromonomerxe2x80x9d of the present invention is any low molecular weight water-insoluble polymer or copolymer having at least one terminal ethylenically unsaturated group that is capable of being polymerized in a free radical polymerization process. The macromonomer of the present invention preferably has xe2x80x9clow water solubilityxe2x80x9d. By xe2x80x9clow water solubilityxe2x80x9d it is meant having a water solubility of no greater than 150 millimoles/liter at 25xc2x0 C. to 50xc2x0 C. In contrast the xe2x80x9cacid containing macromonomerxe2x80x9d, described herein below, of the present invention is water soluble. By xe2x80x9clow molecular weightxe2x80x9d it is meant that the macromonomer has a degree of polymerization of from 5 to 1,000, preferably from 10 to 1,000, more preferably 10 to 200, and most preferably from about 20 to less than 50. By xe2x80x9cdegree of polymerizationxe2x80x9d it is meant the number of polymerized monomer units present in the macromonomer. See e.g., Kawakami in the xe2x80x9cEncyclopedia of Polymer Science and Engineeringxe2x80x9d, Vol. 9, pp. 195-204, John Wiley and Sons, New York, 1987. Typically, the macromonomer polymer chain contains first ethylenically unsaturated monomers, as polymerized units. Preferably, the first ethylenically unsaturated monomer is selected to impart low water solubility to the macromonomer. Although it is most preferred that every unit of macromonomer have at least one terminal ethylenically unsaturated group that is capable of being polymerized in a free radical polymerization process, the percentage of macromonomer units having such a terminal ethylenically unsaturated group is typically sufficient to prepare the desired comb copolymer of the present invention when that percentage is less than 70%, preferably at less than 80%, and more preferably at less than 85%.
The term xe2x80x9cmacromonomer aqueous emulsionxe2x80x9d is used herein to describe an aqueous emulsion containing macromonomer dispersed therein as water insoluble particles.
A xe2x80x9cgraft segmentxe2x80x9d is a polymer chain occupying a pendant position along the polymer backbone. A graft segment may include, as polymerized units, one type of monomer or more than one type of monomer. The composition of a graft segment is different from the composition of the backbone polymer to which it is attached, in contrast to a xe2x80x9cbranch segmentxe2x80x9d of a branched backbone which has a composition which is the same as, or similar to, other portions the branched backbone of which it is a part. A xe2x80x9cterminal graft segmentxe2x80x9d resides at an end of a backbone polymer chain and is chemically attached to that backbone polymer chain. A xe2x80x9cterminal graft segmentxe2x80x9d is a special case of a xe2x80x9cpendant graft segmentxe2x80x9d.
xe2x80x9cGraft copolymersxe2x80x9d are macromolecules formed when polymer or copolymer chains are chemically attached as side chains to a polymeric backbone. Those side chains are the xe2x80x9cgraft segmentsxe2x80x9d described herein above. Because graft copolymers often chemically combine unlike polymeric segments in one macromolecule, these copolymers have unique properties compared to the corresponding random copolymer analogues. These properties include, for example, mechanical film properties resulting from thermodynamically driven microphase separation of the copolymer, and decreased melt viscosities resulting in part from the segmental structure of the graft copolymer, and from separation of a soft (i.e., low Tg) phase. With respect to the latter, reduced melt viscosities can advantageously improve processability of the polymer. See e.g., Hong-Quan Xie and Shi-Biao Zhou, J. Macromol. Sci.-Chem., A27(4), 491-507 (1990); Sebastian Roos, Axel H. E. Mxc3xcller, Marita Kaufmann, Werner Siol and Clenens Auschra, xe2x80x9cApplications of Anionic Polymerization Researchxe2x80x9d, R. P. Quirk, Ed., ACS Symp. Ser. 696, 208 (1998). The graft copolymer of the present invention is a comb copolymer. Herein, the terms xe2x80x9cgraft copolymerxe2x80x9d and xe2x80x9ccomb copolymerxe2x80x9d are used interchangeably.
The term xe2x80x9ccomb copolymer,xe2x80x9d as used herein, is a type of graft copolymer, wherein the polymeric backbone of the graft copolymer is linear, or essentially linear, and, preferably, each side chain (graft segment) of the graft copolymer is formed by a xe2x80x9cmacromonomerxe2x80x9d that is grafted to the polymer backbone. The comb copolymers may, for example, be prepared by the free radical copolymerization of macromonomer with conventional monomer (e.g., second ethylenically unsaturated monomer). Used herein, a comb copolymer may be one, or more than one type of comb copolymer, i.e., at least one comb copolymer.
A xe2x80x9cblock copolymerxe2x80x9d is a copolymer having a backbone characterized by the presence of two or more xe2x80x9cblocksxe2x80x9d. A xe2x80x9cblockxe2x80x9d is a segment of copolymer backbone having a particular and distinct composition. See e.g., G. Odian xe2x80x9cPrinciples of Polymerizationxe2x80x9d, Third Edn., pp. 142-149, John Wiley and Sons, New York, 1991. For example, a block could be composed entirely of styrene monomer, present as polymerized units. At least two blocks differing in composition must be present in a block copolymer, however, more than one block of a given composition may be present. For example, a poly(styrene)-b-poly(butadiene)-b-poly(styrene) has two poly(styrene) blocks joined by a poly(butadiene) block. Blocks are typically at least 10 monomer units, preferably at least 50 monomer units, and more preferably at least 100 monomer units in length. Used herein, the term block copolymer refers to one or more types of block copolymer, i.e., at least one block copolymer.
A xe2x80x9crandom copolymerxe2x80x9d is a copolymer having monomers, as polymerized units, randomly distributed along its backbone. Used herein, the term xe2x80x9crandomxe2x80x9d has its usual meaning in the art of polymerization. For example, the distribution of monomer units along a polymer chain prepared by emulsion polymerization is dictated not only by the relative amounts of each type of monomer present at any point during the polymerization, but also by such factors as, for example, the tendency of each monomer type to react with itself relative to its tendency to react with each of the other types of monomer present. These reactive tendencies are defined by reactivity ratios which are well know for many monomer combinations. See e.g., G. Odian xe2x80x9cPrinciples of Polymerizationxe2x80x9d, Third Edn., pp. 460-492, John Wiley and Sons, New York, 1991.
The term xe2x80x9csegmental copolymerxe2x80x9d includes xe2x80x9cblock copolymersxe2x80x9d and xe2x80x9ccomb copolymersxe2x80x9d. Used herein, the term segmental copolymer refers to one or more types of segmental copolymer, i.e., at least one segmental copolymer.
The term xe2x80x9cSHE copolymerxe2x80x9d refers to a xe2x80x9csoft/hard elastomerxe2x80x9d which is a multi-stage copolymer prepared by sequentially polymerizing, under emulsion polymerization conditions, first monoethylenically unsaturated monomers to yield a first-stage polymer having a Tg of xe2x88x9260xc2x0 C. to xe2x88x9230xc2x0 C., and then polymerizing second monoethylenically unsaturated monomers to yield a second-stage polymer having a Tg of 0xc2x0 C. to 60xc2x0 C. The SHE copolymer further includes low levels (up to 5 percent by weight, based on total copolymer) of either a photosensitive benzophenone or phenylketone compound, or a photosensitive benzophenone monomer, as polymerized units. The SHE copolymers referred to herein are disclosed in U.S. Pat. No. 6,060,532.
An xe2x80x9coligomerxe2x80x9d is a polymer having a low molecular weight. By xe2x80x9clow molecular weightxe2x80x9d it is meant that the oligomer has a degree of polymerization of from 5 to 1,000, preferably from 10 to 1,000, more preferably 10 to 200, and most preferably from about 20 to less than 50.
An xe2x80x9caqueous dispersion of a segmental copolymerxe2x80x9d is an aqueous medium in which are dispersed a plurality of particles of segmental copolymer. Used herein, an xe2x80x9caqueous dispersion of a segmental copolymerxe2x80x9d is an xe2x80x9caqueous copolymer compositionxe2x80x9d.
xe2x80x9cTgxe2x80x9d is the xe2x80x9cglass transition temperaturexe2x80x9d of a polymeric phase. The glass transition temperature of a polymer is the temperature at which a polymer transitions from a rigid, glassy state at temperatures below Tg to a fluid or rubbery state at temperatures above Tg. The Tg of a polymer is typically measured by differential scanning calorimetry (DSC) using the mid-point in the heat flow versus temperature transition as the Tg value. A typical heating rate for the DSC measurement is 20 Centigrade degrees per minute. The Tg of various homopolymers may be found, for example, in Polymer Handbook, edited by J. Brandrup and E. H. Immergut, Interscience Publishers. The Tg of a copolymer is estimated by using the Fox equation (T. G. Fox, Bull. Am. Physics Soc., Volume 1, Issue No. 3, page 123 (1956)). A two-phase system resulting from the formation of a film from a segmental copolymer having two types of segment, each immiscible with the other, typically yields two measurable glass transition temperatures. For such a comb copolymer, one Tg can be measured, or calculated, for the phase formed by the backbone, and another Tg for the phase formed by the graft segment. An xe2x80x9caverage Tgxe2x80x9d, or xe2x80x9coverall Tgxe2x80x9d may be calculated for such systems as a weighted average of the amount of polymer in each phase of a given Tg. This average Tg for a two-phase system will equal the single Tg calculated for a random copolymer having the same overall composition as that of a copolymer for which two Tg values may be calculated or measured.
When a substance (e.g., a coalescent) having some degree of solubility in a polymer is imbibed by that polymer, the softening temperature of the polymer decreases. This plasticization of the polymer can be characterized by measuring the xe2x80x9ceffective Tgxe2x80x9d of the polymer, which typically bears an inverse relationship to the amount of solvent or other substance contained in the polymer. The xe2x80x9ceffective Tgxe2x80x9d of a polymer containing a known amount of a substance dissolved within is measured just as described above for xe2x80x9cTgxe2x80x9d. Alternatively, the xe2x80x9ceffective Tgxe2x80x9d may be estimated by using the Fox equation (supra), assuming a value for Tg (e.g., the freezing point) of the solvent or other substance contained in the polymer.
Synthetic polymers are almost always a mixture of chains varying in molecular weight, i.e., there is a xe2x80x9cmolecular weight distributionxe2x80x9d, abbreviated xe2x80x9cMWDxe2x80x9d. For a homopolymer, members of the distribution differ in the number of monomer units which they contain. This way of describing a distribution of polymer chains also extends to copolymers. Given that there is a distribution of molecular weights, the most complete characterization of the molecular weight of a given sample is the determination of the entire molecular weight distribution. This characterization is obtained by separating the members of the distribution and then quantitating the amount of each that is present. Once this distribution is in hand, there are several summary statistics, or moments, which can be generated from it to characterize the molecular weight of the polymer.
The two most common moments of the distribution are the xe2x80x9cweight average molecular weightxe2x80x9d, xe2x80x9cMwxe2x80x9d, and the xe2x80x9cnumber average molecular weightxe2x80x9d, xe2x80x9cMnxe2x80x9d. These are defined as follows:
Mw=xcexa3(WiMi)/xcexa3Wi=xcexa3(NiMi2)/xcexa3NiMi
Mn=xcexa3Wi/xcexa3(Wi/Mi)=xcexa3(NiMi)/xcexa3Ni
where:
Mi=molar mass of ith component of distribution
Wi=weight of ith component of distribution
Ni=number of chains of ith component
and the summations are over all the components in the distribution. Mw and Mn are typically computed from the MWD as measured by Gel Permeation Chromatography (see the Experimental Section).
xe2x80x9cParticle sizexe2x80x9d is the diameter of a particle.
The xe2x80x9caverage particle sizexe2x80x9d determined for a collection of particles (e.g., macromonomer particles, or particles of graft copolymer) the xe2x80x9cweight average particle sizexe2x80x9d, xe2x80x9cdwxe2x80x9d, as measured by Capillary Hydrodynamic Fractionation technique using a Matec CHDF 2000 particle size analyzer equipped with a HPLC type Ultra-violet detector.
The xe2x80x9cAdvantage termxe2x80x9d, designated xe2x80x9cAxe2x80x9d herein, is a term that defines the performance of an aqueous dispersion of a polymer (herein the polymer is typically a segmental copolymer, preferably a comb copolymer) in a specific test, or a battery of tests, relative to a control, which is an aqueous dispersion of a random copolymer having the same overall composition as the segmental copolymer with which it is being compared. The advantage term for performance in a single test is defined as follows:
A=[(P/Pcontrol)xe2x88x921]xc3x97100%,
where P is the performance of a first material, as an aqueous dispersion, in a given test, and Pcontrol is the performance in the same test of another material, as an aqueous dispersion, with which that first material is being compared. The value of an xe2x80x9cAdvantage termxe2x80x9d is referred to as the corresponding xe2x80x9cAdvantage valuexe2x80x9d, given in units of percent. In determining the value of the Advantage term (i.e., the xe2x80x9cAdvantage valuexe2x80x9d) for an aqueous dispersion of a given segmental copolymer, the control aqueous dispersion is that of a random copolymer having the same overall composition as the segmental copolymer being compared to it, and present in the aqueous dispersion at the same concentration as the segmental copolymer. When the xe2x80x9cAdvantage valuexe2x80x9d for an aqueous dispersion of a polymer-polymer or polymer-oligomer blend is determined herein, the control polymer is an aqueous dispersion of a random copolymer having the same overall composition as the blend. For example, a 50:50 (weight:weight) blend of polymer A composed of, as polymerized units, 30 mole percent of monomer X and 70 mole % of monomer Y, with polymer B composed of, as polymerized units, only monomer Y, would be compared with a random copolymer having 15 mole % of monomer X and 85 mole % of monomer Y.
Four tests measuring xe2x80x9chardnessxe2x80x9d are described herein and utilized to differentiate among various copolymers (as aqueous dispersions) in the Experimental Section herein below. xe2x80x9cAKxe2x80x9d, xe2x80x9cATxe2x80x9d, xe2x80x9cASxe2x80x9d, and xe2x80x9cABxe2x80x9d are the advantage terms derivable from the xe2x80x9cKonig Pendulum Hardnessxe2x80x9d, xe2x80x9cFinger Tackxe2x80x9d, xe2x80x9cTensile Strengthxe2x80x9d, and xe2x80x9cPeel Block Resistancexe2x80x9d tests, respectively. As such, they are referred to as the xe2x80x9cKonig Hardness Advantage termxe2x80x9d, the xe2x80x9cTack Advantage termxe2x80x9d, the xe2x80x9cTensile Strength Advantage termxe2x80x9d, and the xe2x80x9cBlock Advantage termxe2x80x9d, respectively. Used herein, xe2x80x9cKonigxe2x80x9d and xe2x80x9cKonig Hardnessxe2x80x9d may be used interchangeably with xe2x80x9cKonig Pendulum Hardnessxe2x80x9d; xe2x80x9cTackxe2x80x9d may be used interchangeably with xe2x80x9cFinger Tackxe2x80x9d, and xe2x80x9cBlockxe2x80x9d and xe2x80x9cBlock Resistancexe2x80x9d may be used interchangeably with xe2x80x9cPeel Block Resistancexe2x80x9d.
Two tests measuring xe2x80x9csoftnessxe2x80x9d are described herein and utilized to differentiate among various copolymers (as aqueous dispersions) in the Experimental Section herein below. xe2x80x9cAExe2x80x9d, and xe2x80x9cAFxe2x80x9d are the advantage terms derivable from the tensile elongation test and the low temperature mandrel flexibility test, respectively. As such, they are referred to as the xe2x80x9cElongation Advantage termxe2x80x9d and the xe2x80x9cFlexibility Advantage termxe2x80x9d, respectively. The temperature selected for the mandrel flexibility test is chosen to be equal to or less than the overall glass transition temperature, Tg, of the copolymer film being tested. This temperature is chosen, herein, to be xe2x88x9235xc2x0 C., unless specified otherwise.
For any given material, the average of the experimentally determined values for the four xe2x80x9chardnessxe2x80x9d advantage terms are averaged to give the xe2x80x9cHardness Advantage Termxe2x80x9d, xe2x80x9cAHardxe2x80x9d. Similarly, the average of the experimentally determined values for the two xe2x80x9csoftnessxe2x80x9d advantage terms are averaged to give the xe2x80x9cSoftness Advantage Termxe2x80x9d, xe2x80x9cASoftxe2x80x9d. xe2x80x9cAHardxe2x80x9d and xe2x80x9cASoftxe2x80x9d are then averaged to give xe2x80x9cAHSBxe2x80x9d, the xe2x80x9cHard/Soft Balance Advantage termxe2x80x9d, abbreviated herein as xe2x80x9cAHSBxe2x80x9d. The following expressions define xe2x80x9cAHardxe2x80x9d, xe2x80x9cASoftxe2x80x9d, and xe2x80x9cAHSBxe2x80x9d:
xe2x80x83AHard=(AK+AT+AS+AB)/4;
ASoft=(AE+AF)/2; and
AHSB=(AHard+ASoft)/2.
In any equation for an Advantage term used herein to describe performance in a given test, it is assumed that xe2x80x9cPxe2x80x9d and xe2x80x9cPcontrolxe2x80x9d (see the general equation for xe2x80x9cAxe2x80x9d above) are measured by that test method, so that there is no need to provide additional subscripts for those performance terms.
When a material does not form a film under the conditions of film formation used in preparing specimens for the tests, each advantage term is assigned a value of xe2x88x92100%. In such cases, xe2x80x9cAHSBxe2x80x9d also becomes xe2x88x92100%. xe2x80x9cAHSBxe2x80x9d is then a good measure of the three-way balance of film hardness, film softness, and the ability to form a film.
The segmental copolymers of the present invention preferably have Hard/Soft Balance Advantage Values of at least 25%, more preferably from 40% to 1,500%, and most preferably from 100% to 1,000%.
Estimation of whether a polymer and another component (i.e., another polymer or a solvent) will be miscible may be made according to the well-known methods delineated in D. W. Van Krevelen, Properties of Polymers, 3rd Edition, Elsevier, pp. 189-225, 1990. For example, Van Krevelen defines the total solubility parameter (xcex4t) for a substance by:
xcex4t2=xcex4d2+xcex4p2+xcex4h2,
where xcex4d, xcex4p, and xcex4h are the dispersive, polar, and hydrogen bonding components of the solubility parameter, respectively. Values for xcex4d, xcex4p, and xcex4h have been determined for many solvents, polymers, and polymer segments, and can be estimated using the group contribution methods of Van Krevelen. For example, to estimate whether a polymer having a given composition will be miscible with a particular solvent, one calculates xcex4t2 for the polymer and xcex4t2 for the solvent. Typically, if the difference between the two, xcex94xcex4t2, is greater than 25 (i.e., xcex94xcex4t greater than 5), then the polymer and the solvent will not be miscible.
If, instead, it is desired to determine whether two polymers, differing in composition, will be miscible, the same calculations may be carried out, but the predicted upper limit of xcex94xcex4t2 for miscibility will decrease as the molecular weight of one or both of polymers under consideration increases. This decrease is thought to parallel the decrease in entropy of mixing which occurs as the molecular weight of the components being mixed increases. For example, two polymers, each having a degree of polymerization of 100, will likely be immiscible even if the value of xcex94xcex4t2 for their mixture is 9, or even 4 (i.e., xcex94xcex4t=3, or even 2). Still higher molecular weight polymers may be immiscible at even lower values of xcex94xcex4t2. To estimate whether a graft segment of a comb copolymer of the present invention, having a given composition, will be miscible with a backbone having another composition, one calculates xcex4t2 for the graft segment and xcex4t2 for the backbone. Typically, if the difference between the two, xcex94xcex4t2, is greater than 9 (i.e., xcex94xcex4t greater than 3), then the graft segment should be immiscible with the backbone such that a film formed by the comb copolymer would have two distinct types of polymeric phase. It should be noted, however, that immiscibility between two polymers having degrees of polymerization of approximately 100 or more may occur even when the calculated value of xcex94xcex4t2, is between 1 and 9 (i.e., xcex94xcex4t of 1 to 3), due to the unfavorable entropy effects associated with very long polymeric chains. Similar calculation can be performed to determine whether a film formed from a block copolymer will have more than one polymeric phase. Because it is desirable that the graft segment not be miscible with the backbone, the Van Krevelen calculations of miscibility provide useful estimates of whether a given pair of compositions of the graft segment and backbone will result in phase separation in, for example, films formed from the segmental copolymer.
A preferred method of preparing the graft copolymers of the present invention and their aqueous dispersions is by emulsion polymerization. A preferred process for this preparation includes (a) forming, by polymerization of at least one first ethylenically unsaturated monomer, a macromonomer aqueous emulsion containing one or more water-insoluble particles of macromonomer; (b) forming a monomer composition containing at least one second ethylenically unsaturated monomer; and (c) combining at least a portion of the macromonomer aqueous emulsion and at least a portion of the monomer composition to form a xe2x80x9cpolymerization reaction mixturexe2x80x9d. The macromonomer and second ethylenically unsaturated monomer are polymerized in the presence of an initiator to form graft copolymer particles.
The macromonomer of the present invention is present in the macromonomer aqueous emulsion as water insoluble particles. The macromonomer is any low molecular weight water-insoluble polymer or copolymer having at least one terminal ethylenically unsaturated group that is capable of being polymerized in a free radical polymerization process.
The macromonomer contains, as polymerized units, at least one first ethylenically unsaturated monomer. Preferably, the first ethylenically unsaturated monomer is selected to impart low or no water solubility to the macromonomer as previously described herein.
Suitable first ethylenically unsaturated monomers for use in preparing macromonomer include for example methacrylate esters, such as C1 to C18 normal or branched alkyl esters of methacrylic acid, including methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate, stearyl methacrylate; acrylate esters, such as C1 to C18 normal or branched alkyl esters of acrylic acid, including methyl acrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate; styrene; substituted styrenes, such as methyl styrene, a-methyl styrene or t-butyl styrene; olefinically unsaturated nitrites, such as acrylonitrile or methacrylonitrile; olefinically unsaturated halides, such as vinyl chloride, vinylidene chloride or vinyl fluoride; vinyl esters of organic acids, such as vinyl acetate; N-vinyl compounds such as N-vinyl pyrrolidone; acrylamide; methacrylamide; substituted acrylamides; substituted methacrylamides; hydroxyalkylmethacrylates such as hydroxyethylmethacrylate; hydroxyalkylacrylates; basic substituted (meth)acrylates and (meth)acrylamides, such as amine-substituted methacrylates including dimethylaminoethyl methacrylate, tertiary-butylaminoethyl methacrylate and dimethylaminopropyl methacrylamide and the likes; dienes such as 1,3-butadiene and isoprene; vinyl ethers; or combinations thereof. The term xe2x80x9c(meth)xe2x80x9d, i.e., with parentheses, as used herein means that the xe2x80x9cmethxe2x80x9d is optionally present. For example, xe2x80x9c(meth)acrylatexe2x80x9d means methacrylate or acrylate.
The first ethylenically unsaturated monomer can also be a functional monomer including for example monomers containing hydroxy, amido, aldehyde, ureido, polyether, glycidylalkyl, keto functional groups or combinations thereof. These functional monomers are generally present in the macromonomer at a level of from 0.1 weight percent to 15 weight percent and more preferably from 0.5 weight percent to 10 weight percent, and most preferably from 1.0 to 3 weight percent, based on the total weight of the graft copolymer. Used herein, all ranges are inclusive and combinable. Examples of functional monomers include ketofunctional monomers such as the acetoacetoxy esters of hydroxyalkyl acrylates and methacrylates (e.g., acetoacetoxyethyl methacrylate) and keto-containing amides (e.g., diacetone acrylamide); allyl alkyl methacrylates or acrylates; glycidylalkyl methacrylates or acrylates; or combinations thereof. Such functional monomers can provide crosslinking if desired.
Typically, the macromonomer also contains as polymerized units less than 10 weight percent, preferably less than 5 weight percent, more preferably less than 2 weight percent, and most preferably less than less than 1 weight percent acid containing monomer, based on the total weight of the macromonomer. In a most preferred embodiment, the macromonomer contains no acid containing monomer. Used herein, xe2x80x9cacid containing monomerxe2x80x9d and xe2x80x9cacid functional monomerxe2x80x9d are used interchangeably. By xe2x80x9cacid containing monomerxe2x80x9d it is meant any ethylenically unsaturated monomer that contains one or more acid functional groups or functional groups that are capable of forming an acid (e.g., an anhydride such as methacrylic anhydride or tertiary butyl methacrylate). Examples of acid containing monomers include, for example, carboxylic acid bearing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid; acryloxypropionic acid and (meth)acryloxypropionic acid; sulphonic acid-bearing monomers, such as styrene sulfonic acid, sodium vinyl sulfonate, sulfoethyl acrylate, sulfoethyl methacrylate, ethylmethacrylate-2-sulphonic acid, or 2-acrylamido-2-methylpropane sulphonic acid; phosphoethylmethacrylate; the corresponding salts of the acid containing monomer; or combinations thereof.
The macromonomer may contain, as a polymerized unit, a xe2x80x9cnon-methacrylate monomerxe2x80x9d. Used herein, a xe2x80x9cnon-methacrylate monomerxe2x80x9d is any first ethylenically unsaturated monomer that is not a methacrylate. For example, butyl acrylate is a first ethylenically unsaturated monomer that is a non-methacrylate monomer. The macromonomer may be free of non-methacrylate monomer, but typically it contains, as polymerized units, at least one non-methacrylate monomer unit, preferably 5 weight percent to 50 weight percent non-methacrylate monomer, more preferably 10 weight percent to 35 weight percent non-methacrylate monomer, and most preferably 15 weight percent to 25 weight percent of non-methacrylate monomer, based on the weight of the macromonomer.
The macromonomer also contains, as polymerized units, less than 1 mole percent, preferably less than 0.5 mole percent, and more preferably no mercapto-olefin compounds, based on the total moles of monomer, present as polymerized units, in the macromonomer. Used herein, xe2x80x9cmercapto-olefinxe2x80x9d and xe2x80x9cmercaptan-olefinxe2x80x9d are used interchangeably. These mercapto-olefin compounds are those as disclosed in U.S. Pat. No. 5,247,000 by Amick. The mercapto-olefin compounds described in Amick have ester functional groups, which are susceptible to hydrolysis.
In a preferred embodiment of the present invention, the macromonomer is composed of 50 weight percent to 95 weight percent, more preferably from 65 to 90 weight percent, and most preferably from 75 to 85 weight percent, based on total weight of macromonomer, of at least one xcex1-methyl vinyl monomer, a non xcex1-methyl vinyl monomer terminated with an xcex1-methyl vinyl monomer, or combinations thereof. The macromonomer may even be composed of 100 weight percent xcex1-methyl vinyl monomers, non xcex1-methyl vinyl monomers terminated with xcex1-methyl vinyl monomers, or combinations thereof, based on the total weight of the macromonomer. The phrase xe2x80x9cnon xcex1-methyl vinyl monomer terminated with an xcex1-methyl vinyl monomerxe2x80x9d means that, when a vinyl monomer bearing no xcex1-methyl group is present, as polymerized units, in the macromonomer, the macromonomer must be terminated by a unit derived from an xcex1-methyl vinyl monomer. For example, while styrene might be present, as polymerized units, in a macromonomer chain, that macromonomer chain would be terminated by xcex1-methyl styrene, or some other xcex1-methyl vinyl monomer. Suitable xcex1-methyl vinyl monomers include, for example, methacrylate esters, such as C1 to C18 normal or branched alkyl esters of methacrylic acid, including methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, or stearyl methacrylate; hydroxyalkyl methacrylates such as hydroxyethyl methacrylate; glycidylmethacrylate; phenyl methacrylate; methacrylamide; methacrylonitrile; or combinations thereof.
One skilled in the art will recognize that there are many ways to prepare the macromonomer useful in the present invention. For example, the macromonomer may be prepared by a high temperature (e.g., at least 150xc2x0 C.) continuous process such as disclosed in U.S. Pat. No. 5,710,227 or EP-A-1,010,706, published Jun. 21, 2000. In a preferred continuous process, a reaction mixture of first ethylenically unsaturated monomers is passed through a heated zone having a temperature of at least 150xc2x0 C., and more preferably at least 275xc2x0 C. The heated zone may also be maintained at a pressure above atmospheric pressure (e.g., greater than 3,000 kPa=greater than 30 bar). The reaction mixture of monomers may also optionally contain a solvent such as water, acetone, methanol, isopropanol, propionic acid, acetic acid, dimethylformamide, dimethylsulfoxide, methylethylketone, or combinations thereof.
The macromonomer useful in the present invention may also be prepared by polymerizing first ethylenically unsaturated monomers in the presence of a free radical initiator and a catalytic metal chelate chain transfer agent (e.g., a transition metal chelate). Such a polymerization may be carried out by a solution, bulk, suspension, or emulsion polymerization process. Suitable methods for preparing the macromonomer using a catalytic metal chelate chain transfer agent are disclosed in for example U.S. Pat. Nos. 4,526,945, 4,680,354, 4,886,861, 5,028,677, 5,362,826, 5,721,330, and 5,756,605; European publications EP-A-0199,436, and EP-A-0196783; and PCT publications WO 87/03605, WO 96/15158, and WO 97/34934.
Preferably, the macromonomer useful in the present invention is prepared by an aqueous emulsion free radical polymerization process using a transition metal chelate complex. Preferably, the transition metal chelate complex is a cobalt (II) or (III) chelate complex such as, for example, dioxime complexes of cobalt (II), cobalt (II) porphyrin complexes, or cobalt (II) chelates of vicinal iminohydroxyimino compounds, dihydroxyimino compounds, diazadihydroxyiminodialkyldecadienes, or diazadihydroxyiminodialkylundecadienes, or combinations thereof. These complexes may optionally include bridging groups such as BF2, and may also be optionally coordinated with ligands such as water, alcohols, ketones, and nitrogen bases such as pyridine. Additional suitable transition metal complexes are disclosed in for example U.S. Pat. Nos. 4,694,054; 5,770,665; 5,962,609; and 5,602,220. A preferred cobalt chelate complex useful in the present invention is Co II (2,3-dioxyiminobutane-BF2)2, the Co III analogue of the aforementioned compound, or combinations thereof. The spatial arrangements of such complexes are disclosed in for example EP-A-199436 and U.S. Pat. No. 5,756,605.
In preparing macromonomer by an aqueous emulsion polymerization process using a transition metal chelate chain transfer agent, at least one first ethylenically unsaturated monomer is polymerized in the presence of a free radical initiator and the transition metal chelate according to conventional aqueous emulsion polymerization techniques. Preferably, the first ethylenically unsaturated monomer is an xcex1-methyl vinyl monomer as previously described herein.
The polymerization to form the macromonomer is preferably conducted at a temperature of from 20xc2x0 C. to 150xc2x0 C., and more preferably from 40xc2x0 C. to 95xc2x0 C. The solids level at the completion of the polymerization is typically from 5 weight percent to 70 weight percent, and more preferably from 30 weight percent to 60 weight percent, based on the total weight of the aqueous emulsion.
The concentration of initiator and transition metal chelate chain transfer agent used during the polymerization process is preferably chosen to obtain the desired degree of polymerization of the macromonomer. Preferably, the concentration of initiator is from 0.2 weight percent to 3 weight percent, and more preferably from 0.5 weight percent to 1.5 weight percent, based on the total weight of monomer. Preferably, the concentration of transition metal chelate chain transfer agent is from 5 ppm to 200 ppm, and more preferably from 10 ppm to 100 ppm, based on the total monomers used to form the macromonomer.
The first ethylenically unsaturated monomer, initiator, and transition metal chelate chain transfer agent may be added in any manner known to those skilled in the art to carry out the polymerization. For example, the monomer, initiator and transition metal chelate may all be present in the aqueous emulsion at the start of the polymerization process (i.e., a batch process). Alternatively, one or more of the components may be gradually fed to an aqueous solution (i.e., a continuous or semi-batch process). For example, it may be desired to gradually feed the entire or a portion of the initiator, monomer, and/or transition metal chelate to a solution containing water and surfactant. In a preferred embodiment, at least a portion of the monomer and transition metal chelate are gradually fed during the polymerization, with the remainder of the monomer and transition metal chelate being present in the aqueous emulsion at the start of the polymerization. In this embodiment, the monomer may be fed as is, or suspended or emulsified in an aqueous solution prior to being fed.
Any suitable free radical initiator may be used to prepare the macromonomer. The initiator is preferably selected based on such parameters as its solubility in one or more of the other components (e.g., monomers, water); half life at the desired polymerization temperature (preferably a half life within the range of from about 30 minutes to about 10 hours), and stability in the presence of the transition metal chelate. Suitable initiators include for example azo compounds such as 2,2xe2x80x2-azobis (isobutyronitrile), 4,4xe2x80x2-azobis(4-cyanovaleric acid), 2,2xe2x80x2-azobis [2-methyl-N-(1,1-bis(hydroxymethyl)-2-(hydroxyethyl)]-propionamide, and 2,2xe2x80x2-azobis [2-methyl-N-(2-hydroxyethyl)]-propionamide; peroxides such as t-butyl hydroperoxide, benzoyl peroxide; sodium, potassium, or ammonium persulphate or combinations thereof. Redox initiator systems may also be used, such as for example persulphate or peroxide in combination with a reducing agent such as sodium metabisulphite, sodium bisulfite, sodium formaldehyde sulfoxylate, isoascorbic acid, or combinations thereof. Metal promoters, such as iron, may also optionally be used in such redox initiator systems. Also, buffers, such as sodium bicarbonate may be used as part of the initiator system.
An emulsifier is also preferably present during the aqueous emulsion polymerization process to prepare the macromonomer. Any emulsifier may be used that is effective in emulsifying the monomers such as for example anionic, cationic, or nonionic emulsifiers. In a preferred embodiment, the emulsifier is anionic such as for example sodium, potassium, or ammonium salts of dialkylsulphosuccinates; sodium, potassium, or ammonium salts of sulphated oils; sodium, potassium, or ammonium salts of alkyl sulphonic acids, such as sodium dodecyl benzene sulfonate; sodium, potassium, or ammonium salts of alkyl sulphates, such as sodium lauryl sulfate; ethoxylated alkyl ether sulfates; alkali metal salts of sulphonic acids; C12 to C24 fatty alcohols, ethoxylated fatty acids or fatty amides; sodium, potassium, or ammonium salts of fatty acids, such as Na stearate and Na oleate; or combinations thereof. The amount of emulsifier in the aqueous emulsion is preferably from 0.05 weight percent to 10 weight percent, and more preferably from 0.3 weight percent to 3 weight percent, based on the total weight of the monomers.
The macromonomer thus prepared is emulsion polymerized with at least one second ethylenically unsaturated monomer to form a copolymer composition containing graft copolymer particles. The polymerization is carried out by providing the macromonomer as water insoluble particles in a macromonomer aqueous emulsion and the second ethylenically unsaturated monomer in a monomer composition. At least a portion of the macromonomer aqueous emulsion is combined with at least a portion of the monomer composition to form a polymerization reaction mixture that is polymerized in the presence of an initiator.
Although in no way intending to be bound by theory, it is believed that, by providing the macromonomer in the form of water insoluble macromonomer particles in an aqueous emulsion and providing the second ethylenically unsaturated monomer in a separate monomer composition, upon combination the second ethylenically unsaturated monomer diffuses through the aqueous phase and then into the macromonomer particles where the polymerization occurs. Preferably, the diffusion of the second ethylenically unsaturated monomer into the macromonomer particles is evidenced by swelling of the macromonomer particles. Prior to being combined with the monomer composition, the macromonomers are present in plural discrete particles dispersed in the aqueous phase. Preferably, these plural macromonomer particles have previously been formed by aqueous emulsion polymerization, and the resultant macromonomer aqueous emulsion is combined with the monomer composition and subsequently polymerized without being isolated. Addition of the monomer composition to the macromonomer aqueous emulsion results initially in the presence of plural monomer droplets in the aqueous emulsion as separate entities distributed among, but not in direct contact with, the plural macromonomer particles. That is, the monomer droplets are separated from the macromonomer particles, and from each other, by an aqueous phase. Individual monomer molecules must then exit the monomer droplet, dissolve in the aqueous phase, diffuse through that aqueous phase to a macromonomer particle, and enter that macromonomer particle where polymerization to form the graft copolymer (preferably, comb copolymer) occurs. Because the water insoluble macromonomers are unable to diffuse through the aqueous phase, it is essential that the monomer droplets not include water insoluble macromonomer if gel formation is to be avoided and if the number of particles initially established by the macromonomer particles is to be maintained during polymerization of monomers with macromonomers.
The macromonomer aqueous emulsion useful in the present invention may be formed in any manner known to those skilled in the art. For example, the macromonomer, produced by any known method, may be isolated as a solid (e.g., spray dried) and emulsified in water. Also, for example, the macromonomer, if prepared via an emulsion or aqueous based polymerization process, may be used as is, or diluted with water or concentrated to a desired solids level.
In a preferred embodiment of the present invention, the macromonomer aqueous emulsion is formed from the emulsion polymerization of at least one first ethylenically unsaturated monomer in the presence of a transition metal chelate chain transfer agent as described previously herein. This embodiment is preferred for numerous reasons. For example, the macromonomer polymerization can be readily controlled to produce a desired particle size distribution (preferably narrow, e.g., polydispersity less than 2). Also, for example, additional processing steps, such as isolating the macromonomer as a solid, can be avoided, leading to better process economics. In addition, the macromonomer, macromonomer aqueous emulsion, and the graft copolymer can be prepared by consecutive steps in a single reactor which is desirable in a commercial manufacturing facility because process parameters, such as manufacturing cost and particle size distribution, may be optimized.
The xe2x80x9cmacromonomer aqueous emulsionxe2x80x9d useful in the present invention contains from 20 weight percent to 60 weight percent, and more preferably from 30 weight percent to 50 weight percent of at least one water insoluble macromonomer, based on the total weight of macromonomer aqueous emulsion. The macromonomer aqueous emulsion may also contain mixtures of macromonomer. Preferably, the macromonomer aqueous emulsion contains less than 5 weight percent and more preferably less than 1 weight percent of ethylenically unsaturated monomer, based on the total weight of macromonomer aqueous emulsion.
The water insoluble macromonomer particles have a particle size chosen such that, upon addition of monomers, particles of graft copolymer having a desired particle size will be formed. For example, the final graft copolymer particle size is directly proportional to the initial particle size of the macromonomer and the concentration of second ethylenically unsaturated monomer in the polymerization reaction mixture, assuming all the particles participate equally in the polymerization. Preferably, the macromonomer particles have a weight average particle size of from 50 nm to 500 nm, and more preferably from 80 nm to 200 nm as measured by Capillary Hydrodynamic Fractionation technique using a Matec CHDF 2000 particle size analyzer equipped with a HPLC type Ultra-violet detector.
The macromonomer aqueous emulsion may also include one or more emulsifying agents. The type and amount of emulsifying agent is preferably selected in a manner to produce the desired particle size. Suitable emulsifying agents include those previously disclosed for use in preparing the macromonomer by an emulsion polymerization process. Preferred emulsifying agents are anionic surfactants such as, for example, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sulfated and ethoxylated derivatives of nonylphenols and fatty alcohols. The total level of emulsifying agent, based on the total weight of macromonomer is preferably from 0.2 weight percent to 5 weight percent and more preferably from 0.5 weight percent to 2 weight percent.
The xe2x80x9cmonomer compositionxe2x80x9d useful in the present invention contains at least one kind of ethylenically unsaturated monomer. The monomer composition may contain all (i.e., 100%) monomer, or contain monomer dissolved or dispersed in an organic solvent and/or water. Preferably, the level of monomer in the monomer composition is from 50 weight percent to 100 weight percent, more preferably from 60 to 90 weight percent, and most preferably from 70 to 80 weight percent, based on the total weight of the monomer composition. Examples of organic solvents that may be present in the monomer composition include C6 to C14 alkanes. The organic solvent in the monomer composition will be no more than 30 weight percent, and more preferably no more than 5 weight percent, based on the total weight of the monomer composition.
In addition to water and/or organic solvent, the monomer composition may also optionally contain monomers containing functional groups, such as, for example, monomers containing hydroxy, amido, aldehyde, ureido, polyether, glycidylalkyl, keto groups or combinations thereof. These other monomers are generally present in the monomer composition at a level of from 0.5 weight percent to 15 weight percent, and more preferably from 1 weight percent to 3 weight percent based on the total weight of the graft copolymer. Examples of functional monomers include ketofunctional monomers such as the acetoacetoxy esters of hydroxyalkyl acrylates and methacrylates (e.g., acetoacetoxyethyl methacrylate) and keto-containing amides (e.g., diacetone acrylamide); allyl alkyl methacrylates or acrylates; glycidylalkyl methacrylates or acrylates; or combinations thereof. Such functional monomer can provide crosslinking if desired.
In a preferred embodiment, the monomers in the monomer composition are pre-emulsified in water to form a xe2x80x9cmonomer aqueous emulsionxe2x80x9d. Preferably, the monomer aqueous emulsion contains monomer droplets having a droplet size from 0.05 micron to 100 microns, more preferably from 1 micron to 100 microns, and most preferably from 5 microns to 50 microns. Any suitable emulsifying agent may be used, for example those previously described, to emulsify the monomer to the desired monomer droplet size. Preferably, the level of emulsifying agent, if present, will be from 0.2 weight percent to 2 weight percent based on the total weight of monomer in the monomer composition.
The ethylenically unsaturated monomer of the monomer composition is preferably selected to provide the desired properties in the resulting copolymer (e.g., graft copolymer) composition. Suitable ethylenically unsaturated monomers include for example methacrylate esters, such as C1 to C18 normal or branched alkyl esters of methacrylic acid, including methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, isobornyl methacrylate; acrylate esters, such as C1 to C18 normal or branched alkyl esters of acrylic acid, including methyl acrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate; styrene; substituted styrenes, such as methyl styrene, a-methyl styrene or t-butyl styrene; olefinically unsaturated nitriles, such as acrylonitrile or methacrylonitrile; olefinically unsaturated halides, such as vinyl chloride, vinylidene chloride or vinyl fluoride; vinyl esters of organic acids, such as vinyl acetate; N-vinyl compounds such as N-vinyl pyrrolidone; acrylamide; methacrylamide; substituted acrylamides; substituted methacrylamides; hydroxyalkylmethacrylates such as hydroxyethylmethacrylate; hydroxyalkylacrylates; dienes such as 1,3-butadiene and isoprene; vinyl ethers; or combinations thereof. The ethylenically unsaturated monomer can also be an acid containing monomer or a functional monomer, such as those previously described herein. Preferably, the ethylenically unsaturated monomer of the monomer composition does not contain amino groups.
In a preferred embodiment, the monomer composition includes one or more ethylenically unsaturated monomers selected from C1 to C18 normal or branched alkyl esters of acrylic acid, including methyl acrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate; styrene; substituted styrenes, such as methyl styrene, (xcex1-methyl styrene or t-butyl styrene; butadiene or combinations thereof.
As previously mentioned, the macromonomer aqueous emulsion and monomer composition are combined to form a xe2x80x9cpolymerization reaction mixturexe2x80x9d, and polymerized in the presence of a free radical initiator to form an xe2x80x9caqueous copolymer compositionxe2x80x9d, also referred to herein as an xe2x80x9caqueous dispersion of a segmental copolymerxe2x80x9d. The term xe2x80x9cpolymerization reaction mixture,xe2x80x9d as used herein, refers to the resulting mixture formed when at least a portion of the macromonomer aqueous emulsion and at least a portion of the monomer composition are combined. The polymerization reaction mixture may also contain initiator or any other additive used during the polymerization. Thus, the polymerization reaction mixture is a mixture that changes in composition as the macromonomer and monomer in the monomer composition are reacted to form graft copolymer.
The macromonomer aqueous emulsion and monomer composition may be combined in various ways to carry out the polymerization. For example, the macromonomer aqueous emulsion and the monomer composition may be combined prior to the start of the polymerization reaction to form the polymerization reaction mixture. Alternatively, the monomer composition could be gradually fed into the macromonomer aqueous emulsion, or the macromonomer aqueous emulsion could be gradually fed into the monomer composition. It is also possible that only a portion of the macromonomer aqueous emulsion and/or monomer composition be combined prior to the start of the polymerization with the remaining monomer composition and/or macromonomer aqueous emulsion being fed during the polymerization.
The initiator can also be added in various ways. For example, the initiator may be added in xe2x80x9cone shotxe2x80x9d to the macromonomer aqueous emulsion, the monomer composition, or a mixture of the macromonomer aqueous emulsion and the monomer composition at the start of the polymerization. Alternatively, all or a portion of the initiator can be co-fed as a separate feed stream, as part of the macromonomer aqueous emulsion, as part of the monomer composition, or any combination of these methods.
The preferred method of combining the macromonomer aqueous emulsion, the monomer composition, and initiator will depend on such factors as the desired graft copolymer composition. For example, the distribution of the macromonomer as a graft along the backbone can be affected by the concentrations of both the macromonomer and the second ethylenically unsaturated monomers at the time of the polymerization. In this regard, a batch process will afford high concentration of both the macromonomer and the second ethylenically unsaturated monomers at the onset of the polymerization whereas a semi-continuous process will keep the second ethylenically unsaturated monomer concentration low during the polymerization. Thus, through the method by which the macromonomer aqueous emulsion and monomer composition are combined, it is possible to control, for example: the number of graft segments, derived from macromonomer, per polymer chain; the distribution of graft segments in each chain, and the length of the polymer backbone.
Initiators useful in polymerizing the macromonomer and second ethylenically unsaturated monomer include any suitable initiator for emulsion polymerizations known to those skilled in the art. The selection of the initiator will depend on such factors as the initiator""s solubility in one or more of the reaction components (e.g. monomer, macromonomer, water); and half life at the desired polymerization temperature (preferably a half life within the range of from about 30 minutes to about 10 hours). Suitable initiators include those previously described herein in connection with forming the macromonomer, such as azo compounds such as 4,4xe2x80x2-azobis(4-cyanovaleric acid), peroxides such as t-butyl hydroperoxide; sodium, potassium, or ammonium persulfate; redox initiator systems such as, for example, persulphate or peroxide in combination with a reducing agent such as sodium metabisulfite, sodium bisulfite, sodium formaldehyde sulfoxylate, isoascorbic acid; or combinations thereof. Metal promoters, such as iron; and buffers, such as sodium bicarbonate, may also be used in combination with the initiator. Additionally, Controlled Free Radical Polymerization (CFRP) methods such as Atom Transfer Radical Polymerization; or Nitroxide Mediated Radical Polymerization may be used. Preferred initiators include azo compounds such as 4,4xe2x80x2-azobis(4-cyanovaleric acid).
The amount of initiator used will depend on such factors as the copolymer desired and the initiator selected. Preferably, from 0.1 weight percent to 1 weight percent initiator is used, based on the total weight of monomer and macromonomer.
The polymerization temperature will depend on the type of initiator chosen and desired polymerization rates. Preferably, however, the macromonomer and second ethylenically unsaturated monomer are polymerized at a temperature of from 0xc2x0 C. to 150xc2x0 C., and more preferably from 20xc2x0 C. to 95xc2x0 C.
The amount of macromonomer aqueous emulsion and monomer composition added to form the polymerization reaction mixture will depend on such factors as the concentrations of macromonomer and second ethylenically unsaturated monomer in the macromonomer aqueous emulsion and monomer composition, respectively, and the desired graft copolymer composition. Preferably, the macromonomer aqueous emulsion and monomer composition are added in amounts to provide a graft copolymer containing as polymerized units from 2 weight percent to 90 weight percent, more preferably from 5 weight percent to 50 weight percent, and most preferably from 5 weight percent to 45 weight percent macromonomer, and from 10 weight percent to 98 weight percent, more preferably from 50 weight percent to 95 weight percent and most preferably from 55 weight percent to 95 weight percent second ethylenically unsaturated monomer.
One skilled in the art will recognize that other components used in conventional emulsion polymerizations may optionally be used in the method of the present invention. For example, to reduce the molecular weight of the resulting graft copolymer, the polymerization may optionally be conducted in the presence of one or more chain transfer agents, such as n-dodecyl mercaptan, thiophenol; halogen compounds such as bromotrichloromethane; or combinations thereof. Also, additional initiator and/or catalyst may be added to the polymerization reaction mixture at the completion of the polymerization reaction to reduce any residual monomer, (e.g., chasing agents). Suitable initiators or catalysts include those initiators previously described herein. In addition, the chain transfer capacity of a macromonomer through addition-fragmentation can be utilized in part to reduce molecular weight through appropriate design of monomer compositions and polymerization conditions. See e.g., E. Rizzardo, et. al., Prog. Pacific Polym. Sci., 1991, 1, 77-88; G. Moad, et. al., WO 96/15157.
Preferably, the process of the present invention does not require neutralization of the monomer, or resulting aqueous graft copolymer composition. These components preferably remain in unneutralized form (e.g., no neutralization with a base if acid functional groups are present).
The resulting aqueous comb copolymer composition formed by polymerization of the macromonomer and the ethylenically unsaturated monomer in the monomer composition preferably has a solids level of from 30 weight percent to 70 weight percent and more preferably from 40 weight percent to 60 weight percent. The aqueous comb copolymer composition contains comb copolymer particles preferably having a weight average particle size of from 50 nm to 1,000 nm, more preferably from 60 nm to 500 nm, and most preferably from 80 nm to 200 nm.
The graft copolymer formed preferably has a backbone containing, as polymerized units, the second ethylenically unsaturated monomer from the monomer composition, and one or more macromonomer units, as polymerized units, wherein a terminal ethylenically unsaturated group of the macromonomer is incorporated into the backbone and the remainder of the macromonomer becomes a graft segment pendant to the backbone (i.e., a side chain) upon polymerization. Preferably, each side chain is a graft segment derived from the grafting of one macromonomer to the backbone.
The degree of polymerization of the graft segments derived from the macromonomer is preferably from 5 to 1,000, preferably from 10 to 1,000, more preferably 10 to 200, and most preferably from 20 to less than 50, where the degree of polymerization is expressed as the number of polymerized units of ethylenically unsaturated monomer used to form the macromonomer. The weight average molecular weight of the graft copolymer (e.g., of the comb copolymer) is preferably in the range of from 50,000 to 2,000,000, and more preferably from 100,000 to 1,000,000. Weight average molecular weights as used herein can be determined by size exclusion chromatography.
The graft copolymer particles of the aqueous graft copolymer composition can be isolated, for example, by spray drying or coagulation, followed by forming a coating by powder coating methods, or by redispersing in an aqueous medium. However, it is preferable to use the aqueous copolymer composition (i.e., the aqueous dispersion of segmental copolymer) without an intermediate isolation step to form a film.
In a preferred embodiment of the present invention, the polymerization is conducted in two stages. In the first stage, the macromonomer is formed in an aqueous emulsion polymerization process, and in the second stage the macromonomer is polymerized with the second ethylenically unsaturated monomer in an emulsion. For efficiency, preferably these two stages are conducted in a single vessel. For example, in the first stage, the macromonomer aqueous emulsion may be formed by polymerizing in an aqueous emulsion at least one first ethylenically unsaturated monomer to form water insoluble macromonomer particles. This first stage polymerization is preferably conducted using a transition metal chelate chain transfer agent as previously described herein. After forming the macromonomer aqueous emulsion, a second emulsion polymerization is preferably performed in the same vessel to polymerize the macromonomer with at least one second ethylenically unsaturated monomer. This second stage may be conducted for example by directly adding (e.g., all at once or by a gradual feed) the monomer composition and initiator to the macromonomer aqueous emulsion. One main advantage of this embodiment is that the macromonomer does not have to be isolated, and the second polymerization can take place simply by adding the monomer composition and initiator to the macromonomer aqueous emulsion. In this preferred embodiment, the particle size and particle size distribution of the plural water insoluble macromonomer particles may be precisely controlled, and later addition of more macromonomer aqueous emulsion would typically not be required, except when, for example, a second mode (particle size and/or composition) of graft copolymer is desired.
In another preferred embodiment of the present invention, the polymerization of the macromonomer and second ethylenically unsaturated monomer is at least partially performed in the presence of an acid containing monomer, acid containing macromonomer, or combinations thereof. The acid containing monomer or acid containing macromonomer may be added in any manner to the polymerization reaction mixture. Preferably, the acid containing monomer or acid containing macromonomer is present in the monomer composition. The acid containing monomer or acid containing macromonomer may also be added as a separate stream to the polymerization reaction mixture.
The amount of acid containing monomer or acid containing macromonomer added to the polymerization reaction mixture is preferably from 0.2 weight percent to 10 weight percent, more preferably from 0.5 weight percent to 5 weight percent, and most preferably from 1 weight percent to 2 weight percent, based on the total weight of monomer and macromonomer added to the polymerization reaction mixture.
Acid containing monomers which may be used in this embodiment include ethylenically unsaturated monomers bearing acid functional or acid forming groups such as those previously described herein. The xe2x80x9cacid containing macromonomerxe2x80x9d useful in this embodiment is any low molecular weight polymer having at least one terminal ethylenically unsaturated group that is capable of being polymerized in a free radical polymerization process, and that is formed from at least one kind of acid containing monomer. Preferably, the amount of acid containing monomer present, as polymerized units, in the acid containing macromonomer is from 50 weight percent to 100 weight percent, more preferably from 90 weight percent to 100 weight percent, and most preferably from 95 weight percent to 100 weight percent.
The acid containing macromonomer may be prepared according to any technique known to those skilled in the art such as those previously described herein. In a preferred embodiment of the present invention, the acid containing macromonomer is prepared by a solution polymerization process using a free radical initiator and transition metal chelate complex. Such a process is disclosed in, for example, U.S. Pat. No. 5,721,330. Preferred acid containing monomers used to form the acid containing macromonomer are xcex1-methyl vinyl monomers such as methacrylic acid.
In another preferred embodiment of the present invention, a xe2x80x9cmacromolecular organic compoundxe2x80x9d having a hydrophobic cavity is present in the polymerization medium used to form the macromonomer and/or aqueous copolymer composition. Although the macromolecular organic compound may be used to facilitate transport of any ethylenically unsaturated monomer through the aqueous phase of the polymerization reaction mixture, preferably, the macromolecular organic compound is used when copolymerizing ethylenically unsaturated monomers with a water solubility of no greater than 150 millimoles/liter, more preferably no greater than 50 millimoles/liter. Herein, a water solubility at 25xc2x0 C. to 50xc2x0 C. of no greater than 50 millimoles/liter is referred to as xe2x80x9cvery low water solubilityxe2x80x9d. Ethylenically unsaturated monomers having very low water solubility include, for example, lauryl (meth)acrylate and stearyl (meth)acrylate. The macromolecular organic compound may, for example, be added to the monomer composition, the macromonomer aqueous emulsion, or the polymerization reaction mixture used to form the aqueous copolymer composition. Also, for example, the macromolecular organic compound may be added to an aqueous emulsion of ethylenically unsaturated monomer used to form the macromonomer. Suitable techniques for using a macromolecular organic compound having a hydrophobic cavity are disclosed in, for example, U.S. Pat. No. 5,521,266.
Preferably, the macromolecular organic compound having a hydrophobic cavity is added to the polymerization reaction mixture to provide a molar ratio of macromolecular organic compound to very low water solubility monomer or macromonomer of from 5:1 to 1:5000 and more preferably from 1:1 to 1:500.
Macromolecular organic compounds having a hydrophobic cavity useful in the present invention include for example cyclodextrin or cyclodextrin derivatives; cyclic oligosaccharides having a hydrophobic cavity such as cycloinulohexose, cycloinuloheptose, or cycloinuloctose; calyxarenes; cavitands; or combinations thereof. Preferably, the macromolecular organic compound is xcex2-cyclodextrin, more preferably methyl-xcex2-cyclodextrin.
Monomers having low water solubility include for example primary alkenes; styrene and alkylsubstituted styrene; xcex1-methyl styrene; vinyltoluene; vinyl esters of C4 to C30 carboxylic acids, such as vinyl 2-ethylhexanoate, vinyl neodecanoate; vinyl chloride; vinylidene chloride; N-alkyl substituted (meth)acrylamide such as octyl acrylamide and maleic acid amide; vinyl alkyl or aryl ethers with (C3-C30) alkyl groups such as stearyl vinyl ether; (C1-C30) alkyl esters of (meth)acrylic acid, such as methyl methacrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate; unsaturated vinyl esters of (meth)acrylic acid such as those derived from fatty acids and fatty alcohols; multifunctional monomers such as pentaerythritol triacrylate; monomers derived from cholesterol or combinations thereof.
In another aspect of the present invention an xe2x80x9caqueous copolymer compositionxe2x80x9d is provided that is preferably produced by the method of the present invention as previously described herein. The aqueous copolymer composition contains a plurality of water insoluble particles of graft copolymer that are preferably comb copolymer particles. The comb copolymer particles preferably have a weight average particle size of from 50 nm to 1,000 nm, more preferably from 60 nm to 500 nm, and most preferably from 80 nm to 200 nm.
Preferably, the particles of graft copolymer contain from 2 weight percent to 90 weight percent, and more preferably from 5 weight percent to 50 weight percent polymerized units of a macromonomer, based on the total weight of the copolymer, where the macromonomer preferably has a composition as previously described herein for the water insoluble macromonomer present in the macromonomer aqueous emulsion. The graft copolymer particles also preferably contain from 10 weight percent to 98 weight percent, and more preferably from 50 weight percent to 95 weight percent polymerized units of at least one second ethylenically unsaturated monomer, based on the total weight of the copolymer. The ethylenically unsaturated monomer may be any ethylenically unsaturated monomer that provides desirable properties in the copolymer particles, such as those useful in the monomer composition as previously described herein.
Preferably, the backbone of the graft copolymer is linear. Compositionally, the backbone of the copolymer preferably contains polymerized units of the scond ethylenically unsaturated monomer derived from the monomer composition. Preferably, the backbone contains less than 20 mole percent, and more preferably less than 10 mole percent of polymerized macromonomer derived from the macromonomer aqueous emulsion, based on the total moles of monomer, as polymerized units, in the copolymer. Preferably, the Tg of the backbone is from xe2x88x9290xc2x0 C. to 50xc2x0 C., more preferably xe2x88x9280xc2x0 C. to 25xc2x0 C., and most preferably xe2x88x9260xc2x0 C. to 0xc2x0 C. The pendant graft segments of the graft copolymer preferably contain polymerized units of the macromonomer. The carbon atoms of the double bond of the macromonomer, and other atoms such a hydrogen and groups such as methyl directly attached to those carbon atoms, become, as a polymerized unit, part of the backbone of the graft copolymer, while the remainder of the macromonomer becomes a graft segment of the graft copolymer. In a preferred embodiment of the present invention, each graft segment is derived from one macromonomer. The graft segment contains as polymerized units less than 10 weight percent, preferably less than 5 weight percent, more preferably less than 2 weight percent and most preferably less than 1 weight percent acid containing monomer, based on the weight of the macromonomer from which it was derived. In a most preferred embodiment, the graft segment contains no acid containing monomer. Further, the graft segment may be free of non-methacrylate monomer, but typically contains, as polymerized units, at least one molecule of non-methacrylate monomer, preferably 5 weight percent to 50 weight percent non-methacrylate monomer, more preferably 10 weight percent to 35 weight percent non-methacrylate monomer, and most preferably 15 weight percent to 25 weight percent of non-methacrylate monomer, based on the weight of the macromonomer from which it was derived. Additionally, the pendant graft segments contain less than 5 weight percent and more preferably less than 1 weight percent of the polymerized second ethylenically unsaturated monomer derived from the monomer composition, based on the total weight of the pendant graft segments.
Preferably, the Tg of the graft segment is from 30xc2x0 C. to 130xc2x0 C., more preferably from 40xc2x0 C. to 120xc2x0 C., and most preferably from 50xc2x0 C. to 105xc2x0 C.
Preferably, the graft segment is present in the graft copolymer at from 1 weight percent to 70 weight percent, more preferably 2 to 45 weight percent, and most preferably 5 to 35 weight percent, based on the weight of the comb copolymer, where the weight of the graft segment is taken as the weight of the macromonomer from which the graft segment was derived.
Preferably, the overall weight average molecular weight of the graft copolymer is from 50,000 to 2,000,000, and more preferably from 100,000 to 1,000,000.
In a preferred embodiment of the present invention, the water insoluble graft copolymer particles further contain from 0.2 weight percent to 10 weight percent, more preferably from 0.5 weight percent to 5 weight percent, and most preferably from 1 weight percent to 2 weight percent of an acid containing macromonomer, based on the total weight of the graft copolymer. The acid containing macromonomer preferably has a composition as previously described herein.
Although in no way intending to be bound by theory, it is believed that the xe2x80x9cacid containing macromonomerxe2x80x9d is attached to the surface of the water insoluble graft copolymer particles and provides stability. By xe2x80x9cattached,xe2x80x9d as used herein, it is believed that the acid containing macromonomer is bound in some manner (e.g., covalent, hydrogen bonding, ionic) to a polymer chain in the particle. Preferably, the acid containing macromonomer is covalently bound to a polymer chain in the particle. The acid containing macromonomer is most effective when present at the surface of the graft copolymer particle. As such, it is not necessary that even one acid containing macromonomer unit be incorporated into every graft compolymer. In fact, it is preferable that, when units of acid containing macromonomer are attached to chains of graft copolymer, those chains are at the surface of the graft copolymer particles. It has been found that the acid containing macromonomer provides stability to the particles such that the aqueous copolymer composition produced exhibits unexpected improved shear stability; freeze thaw stability; and stability to additives in formulations, as well as reduction of coagulum during the polymerization. Although improved stability can be achieved using acid containing monomer, these benefits are most dramatic when an acid containing macromonomer is used.
The aqueous copolymer composition in addition to the copolymer particles preferably contains less than 10 weight percent, and more preferably less than 1 weight percent of organic solvent, based on the weight of copolymer particles. In a most preferred embodiment, the aqueous copolymer composition contains no organic solvent.
An advantage of using the method of the present invention to prepare the aqueous copolymer composition is that the resulting copolymer composition contains low levels of homopolymer, such as for example homopolymer of second ethylenically unsaturated monomer derived from the monomer composition or homopolymer of macromonomer derived from the macromonomer aqueous emulsion. Preferably the aqueous copolymer composition contains less than 30 weight percent and more preferably less than 20 weight percent of homopolymer of macromonomer, based on the total weight of the graft copolymer. Preferably also the aqueous copolymer composition contains less than 30 weight percent and more preferably less than 20 weight percent of homopolymer of ethylenically unsaturated monomer.
The aqueous dispersion of the present invention may include a coalescent. The coalescent of the present invention may be any coalescent known to the art. For example, many common solvents are use in the art as coalescents. It is preferred that the coalescent is present in the amount of from 0 weight percent to 40 weight percent, more preferably 0 weight percent to 20 weight percent, and most preferably 0 weight percent to 5 weight percent, based on the weight of the comb copolymer. In a most preferred embodiment, the aqueous coating composition contains no coalescent. The aqueous dispersion of the present invention may further contain an emulsion polymer not meeting the limitations of the segmental copolymer of the present invention, including a film-forming and/or a non-film-forming emulsion polymer. This emulsion polymer may be introduced by blending or in-situ polymerization. When included in the aqueous dispersion, the emulsion polymer not meeting the limitations of the comb copolymer of the present invention is preferably present in an amount of from 1 weight percent to 99 weight percent, more preferably 5 weight percent to 95 weight percent, and most preferably 10 weight percent to 90 weight percent, based on the combined weight of the comb copolymer and the emulsion polymer not meeting the limitations of the comb copolymer of the present invention.
The aqueous copolymer compositions produced by the method of the present invention are useful in a variety of applications. For example, the aqueous copolymer compositions may be used in architectural and industrial coatings including paints, wood coatings, or inks; paper coatings; textile and nonwoven binders and finishes; adhesives; mastics; asphalt additives; floor polishes; leather coatings; plastics; plastic additives; petroleum additives; thermoplastic elastomers or combinations thereof.
When the aqueous copolymer compositions of the present invention are used as coatings compositions, it is often desirable to have additional components added to the coating composition to form the final formulation for coating compositions, including traffic paints, described herein. These additional components include, for example, thickeners; rheology modifiers; dyes; sequestering agents; biocides; dispersants; pigments, such as, titanium dioxide, organic pigments, carbon black; extenders, such as calcium carbonate, talc, clays, silicas and silicates; fillers, such as glass or polymeric microspheres, quartz and sand; anti-freeze agents; plasticizers; adhesion promoters such as silanes; coalescents; wetting agents; surfactants; slip additives; crosslinking agents; defoamers; colorants; tackifiers; waxes; preservatives; freeze/thaw protectors; corrosion inhibitors; and anti-flocculants. During application of the aqueous coating composition of the present invention to the surface of a substrate, glass or polymeric microspheres, quartz and sand may be added as part of the that coating composition or as a separate component applied to the surface in a separate step simultaneously with, before, or after the step of application of the aqueous coating composition.
The aqueous copolymer compositions produced by the method of the present invention are useful in a variety of applications. For example, the aqueous copolymer compositions may be used in architectural and industrial coatings including paints, wood coatings, or inks; paper coatings; textile and nonwoven binders and finishes; adhesives; mastics; floor polishes; leather coatings; plastics; plastic additives; petroleum additives; thermoplastic elastomers or combinations thereof.